ESPE Abstracts

Circadian clock system is an evolutionarily conserved system, by which organisms adapt their metabolic activities to environmental inputs including nutrient availability. The master pacemaker of the clock system is located in the suprachiasmatic nucleus (SCN) in the hypothalamus. The neurons in the SCN are entrained by the signals from the light through the retinal-hypothalamic tract and the light-dark cycle of the environment creates the rhythmic patterning of behavioral and physiological rhythmicity. In addition to the central pacemaker, peripheral tissues also possess their own circadian network and synchronize with the central clock system through hormonal and neuronal signals. Organisms utilize this system to maximize the efficiency of time-of-day–dependent utilization of ingested nutrients by optimizing the metabolic processes in peripheral tissues; therefore, the disruption of this system has been pathogenically linked to the disintegration of metabolic homeostasis including skeletal metabolism. These findings point to the important role of circadian clock system as a nodal point to link nutrient availability and metabolism. Calcium is a critical nutrient involved in skeletal metabolism, and circulating calcium levels are known to have daily rhythms in human, indicating that calcium homeostasis is under the regulation of circadian clock system; however, this has not been well studied so far. Based on this background, the speaker has been investigating the role for circadian clock system in calcium homeostasis using a mouse model in which intestinal circadian clock system is disrupted, and found that intestinal clock network regulates calcium absorption in a time dependent manner, which results in the disintegration of skeletal homeostasis. In this talk, the speaker would like to present current findings how calcium homeostasis is regulated by circadian clock system and its influence on skeletal metabolism.